XML 38 R25.htm IDEA: XBRL DOCUMENT
v3.4.0.3

Investments (Tables) | 3 Months Ended
--- | ---
Mar. 31, 2016
Investments [Abstract] |
Other Investments [Table Text Block] |
Other Investments | March 31, 2016 |  |  | December 31, 2015 |
Millions |  |  |
ALLETE Properties |  | $49.1 |  |  |  | $50.1 |
Available-for-sale Securities (a) | 17.4 |  |  | 18.5 |
Cash Equivalents | 2.5 |  |  | 2.0 |
Other | 3.9 |  |  | 4.0 |
Total Other Investments |  | $72.9 |  |  |  | $74.6 |
(a) | As of March 31, 2016, the aggregate amount of available-for-sale corporate debt securities maturing in one year or less was zero, in one year to less than three years was $1.6 million, in three years to less than five years was $4.1 million, and in five or more years was $4.7 million.

X
- Definition A table of investments, shown as a text block. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Article 6 -Section 10 -Paragraph (c) -Subparagraph (1) + Details
Name: | invest_InvestmentTableTextBlock
Namespace Prefix: | invest_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- References No definition available. + Details
Name: | us-gaap_InvestmentsAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration